Libwda with frontier support

[marcmengel]

This is for a new version of libwda that will support frontier: URL's with frontier_client.
I'm making this a draft until and if Alex Rahe completes this work as the -D values etc.
are my guesses and not his. Also not sure if we want to make this a variant when it's done
or just have it always depend on frontier_client.

[knoepfel]

@marcmengel, do you expect this variant to be routinely used by Fermilab experiments? Or is this just a variant to be used by Alex and others?

[marcmengel]

Initially the latter; however this is functionality that could be useful to collaborations like Dune who might want to access databases other than the conditions databases ( which have existing web-api's ) in analysis / grid jobs, at which point
we might make it the default.

[knoepfel]

Understood, @marcmengel. Should this PR still be in draft mode?

[knoepfel]

@marcmengel, any update on this PR?

[marcmengel]

So this had somewhat slipped my mind; thanks for the reminder. I'm trying to schedule a get-together with
Alex, who is doing this libwda update, to try this out. If it looks good, then I'll put it out of draft mode.